This invention relates generally to flash-producing electrical circuits for use with a flash lamp device and more particularly, it relates to an improved flash strobe power supply having energy storage devices and a trigger timing circuit for the respective charging and firing of a flash lamp disposed remotely therefrom without the effects of neoning, saturation and overcharging.
Heretofore, flash lamp assemblies have been generally made as an integral unit housing all of the associated electronic components therein. These electronic components would include main storage means for providing the main supply potential or flash-producing voltage applied to the two principal electrodes of a flash tube as well as a timing or firing means for producing trigger impulses applied to the trigger electrode of the flash tube. The timing means includes a trigger capacitor with a resistor and a switching device. In such conventional flash lamp assemblies of the prior art, all three electrodes (the two principal electrodes and trigger electrodes) must be connected to external circuity and thus could not be simply inserted into a conventional incandescent lamp socket which has only a two-contact receptacle.
A new improved flash lamp assembly is disclosed in U.S. patent application Ser. No. 376,752 entitled "Flash Lamp" filed on May 10, 1982 which has now matured into U.S. Pat. No. 4,463,282 issued on July 31, 1984, and assigned to the assignee as the present application, which has eliminated the main storage means and timing means from its internal housing. This improved flash lamp in Ser. No. 376,752 requires both an external trigger timing means and storage means for providing main supply potential and is adapted to permit its insertion into an incandescent lamp receptacle having only the two-contact receptacle. We have discovered a new and improved flash strobe power supply having energy storage devices and a trigger timing means for driving the new flash lamp assembly disclosed in the said copending application.
In the art of flash tubes, it is known that if the voltage applied between the principal electrodes of a flash tube is below a certain level or minimum starting voltage, the discharge of a singular "flash" of radiant energy across the spark gap will not be initiated regardless of how high the potential of the trigger impulse is. Therefore, the flash tube required an electric power supply capable of charging an energy storage device such as a flash capacitor with a voltage higher than the minimum starting voltage. However, if the power source contains excess energy in magnitude or the flash capacitor is charged during the time of the flash, the flash could fail to extinguish after the single flash and produce radiant energy continuously. This effect is referred to as "neoning" by those skilled in the art.
Flash tubes nowadays have a trigger electrode that can be energized to produce sufficient energy to flash the tube at a somewhat lower applied voltage, but still requires a voltage in the order of 160 to 200 D.C. volts. This may cause unsafe or harmful operating conditions due to the increased probability of occurrence of electric shocks at these high voltage levels. Therefore, it would be desirable to provide a flash strobe power supply which could accommodate a relatively low battery voltage of 12 or 24 D.C. volts so as to avoid any dangers.
With the recent development of "double flash" flash tubes where two or more flashes are generated over a short period of time and separated by a longer time delay and then followed by two or more flashes to produce the effect of a single flash of longer duration or a pair of individual flashes closely spaced together, prior art power supplies have used the same flash capacitor circuit for producing the second flash that powered the first flash. These prior art power supplies suffered from the disadvantage in causing the "neoning" problem to occur in the flash tube due to the subsequent recharging of the same capacitor. It would be desirable to have a new power supply with independently charged capacitors for producing each of the first and second flashes.
In other prior art systems which employ an inverter-type power supply having a transformer for transferring stored energy to a capacitor to fire a flash lamp, the oscillation cycle was established by operating the transformer into saturation. However, since the inductance of the transformer is minimum at saturation optimum energy was not obtained and significant loss occurred due to thermal dissipation by heating of the transformer. An additional problem encountered in the prior art is the allowance of the storage capacitors to continue to increase without limit to a level which could cause damage or destruction to the flash tube.
The power supply of the present invention is capable of providing charged flash voltages and trigger pulses for a flash tube which overcomes all of the above-discussed disadvantages. The power supply is adapted to provide repeatedly either a singular "flash" of radiant energy alternatingly to a pair of flash lamps or a "double flash" of radiant energy to a single flash tube which eliminates the problems of neoning in the flash tubes, saturating of the inverter transformer, and overcharging of the storage capacitors.